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采用椭偏法测量入射光波长为0.632μm,入射角为50°~85°时合金钢的光学常数。考虑材料表面的粗糙度,用Ohlidal-Lukes理论对所测光学常数值进行了修正,发现椭偏参量的修正量随入射角增大而增大。结果表明,测量入射角在50°~70°范围内测量值与修正后计算结果基本一致,在70°~85°范围内测量值与修正后的计算结果差距较大。因此,用椭偏法测量合金钢光学常数时使入射角小于70°,测量结果会更加准确。 相似文献
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本文从理论上阐述了采用最大偏向角法测量光学玻璃常数的方法。推导出计算原理公式,并分析了色散的测量误差,其测试精度为±1.0×10~(-8)。其次,简要地讲述了样品的制备要求和测试方法。 相似文献
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一种基于移相误差估计的5步移相算法 总被引:1,自引:0,他引:1
移相误差是用移相法进行相位测量的主要误差。本文提出一种 5步移相算法 ,分两步进行相位计算 ,首先估计实际步进移相的线性移相误差 ,然后再利用此移相误差估计值计算相位分布。移相误差估计公式和相位计算公式简洁 ,算法简单易行 ,对线性移相误差和二次谐波的敏感度低 ,可基本消除线性移相误差对解调相位的影响。对本文提出的算法进行了仿真研究 ,同时给出了 Hariharan 5步算法、Surrel 6步最小算法的仿真结果。结果表明 :本算法明显优于以上两种算法 ,可基本消除线性移相误差引起的相位偏移。本算法适用于作等步移相的相位测量或移相的标定。 相似文献
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全场数字化测量光弹性等倾角的五步彩色相移法 总被引:8,自引:1,他引:7
通过把相移法与光学彩色信息图像处理技术相结合 ,提出了一种确定全场光弹性等倾角的五步彩色相移法。模型置于白光照射下 ,在起偏镜与分析镜不同设置的平面偏振光场中 ,用彩色数码照相机分别采集五幅等色线与等倾线相耦合的条纹图 ,根据相移法基本原理 ,就可以确定在 0~π/2范围内的等倾角。经过对径压缩圆盘的检验 ,实验结果与理论完全相符。该方法改进了单色光相移法的不足 ,对实验应力分析及其在工程结构强度设计中的应用将起积极的促进作用 相似文献
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Combining color imaging with phase shifting, a technique named five-step color phase shifting is presented to determine the whole-field isoclinic parameter. Relevant theory is derived and explicit conditions for directly determining the isoclinic parameter in the range of [0,π/2] are given. The unloaded light intensity of the model is systematically studied. A color camera recorded five isoclinic images coupled with isochromatics from a plane polariscope with five different settings, respectively. Experiments have been carried out with a circular disk under diametral compression and errors have been analyzed and estimated. This technique utilizes white light, which avoids undefined isoclinics near the locations where the isochromatics exist and will have active effect on experimental stress analysis and structural strength design. 相似文献
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数字光弹性中五步彩色相移法及其应用 总被引:1,自引:1,他引:0
把相移法与光学彩色信息图像处理技术相结合,提出全场数字化确定主方向角的光弹性五步彩色相移法。其主要优点是采用最简单的白光平面偏振仪光学系统,由数码照相机采集五幅等色线与等倾线相互耦合的彩色条纹图,经计算机进行处理后,就可以得到[O~π/2]范围内单纯连续的等倾角相图;为了减少测量误差,在相移法中引入背景光强参与运算。对实验中存在的三种主要误差因素进行了定量分析,给出了具体的误差控制指标。用对径压缩圆盘问题的理论仿真模拟结果、基本实验和复杂平面及空间实际问题进行检验和对比,表明本方法是正确可行的。 相似文献
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In photoelasticity, the method of obtaining the individual values of principal stresses/normal stresses separately is referred to as stress separation. Shear difference is one of the widely used techniques for stress separation in photoelasticity and one needs the value of fringe order and the isoclinic angle free of noise at every pixel over the domain. For accurate parameter determination, a ten-step phase shifting approach which uses a plane polariscope for isoclinic determination and a circular polariscope for isochromatic determination is proposed. A new quality guided approach for isoclinic unwrapping is developed. Isochromatic phasemap free of ambiguous zones is obtained by a new methodology and is unwrapped by a quality-guided approach. Whole field evaluation of stress components and its representation is then presented. The models used in this study are intentionally subjected to moderate loads showing a high level of isochromatic–isoclinic interaction. In view of this, the isoclinic data has several kinks which is found to cause streak formation in the whole field representation of separated stress components. An outlier smoothing algorithm is proposed for getting a smooth variation of the digital photoelastic parameters over the domain. Use of such smoothed data for stress separation has removed the streaks and has also greatly improved the accuracy of the separated stress components. 相似文献
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Phase shifting photoelasticity in white light 总被引:1,自引:0,他引:1
Augusto Ajovalasit Giovanni Petrucci Michele Scafidi 《Optics and Lasers in Engineering》2007,45(5):596
The availability of image acquisition systems has led to the development of digital photoelasticity both in monochromatic and white light. In particular white light has been used mainly with the following methods: Spectral Content Analysis, RGB photoelasticity and phase shifting photoelasticity. Phase shifting photoelasticity in the colour domain has been used effectively for the determination of the isoclinic parameter in order to reduce the influence of the isochromatic fringes. The method has been also proposed for the determination of the isochromatic fringe order. This paper concerns the general characteristics of phase shifting photoelasticity in the colour domain. Special attention is drawn towards the influence of spectral content of the light source, the spectral response of the colour camera filters, the dispersion of the birefringence and the error of quarter wave plates. 相似文献
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In this work, digital photoelasticity technique is used to estimate the crack tip fracture parameters for different crack configurations. Conventionally, only isochromatic data surrounding the crack tip is used for SIF estimation, but with the advent of digital photoelasticity, pixel-wise availability of both isoclinic and isochromatic data could be exploited for SIF estimation in a novel way. A linear least square approach is proposed to estimate the mixed-mode crack tip fracture parameters by solving the multi-parameter stress field equation. The stress intensity factor (SIF) is extracted from those estimated fracture parameters. The isochromatic and isoclinic data around the crack tip is estimated using the ten‐step phase shifting technique. To get the unwrapped data, the adaptive quality guided phase unwrapping algorithm (AQGPU) has been used. The mixed mode fracture parameters, especially SIF are estimated for specimen configurations like single edge notch (SEN), center crack and straight crack ahead of inclusion using the proposed algorithm. The experimental SIF values estimated using the proposed method are compared with analytical/finite element analysis (FEA) results, and are found to be in good agreement. 相似文献